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	<title>类选择器</title>
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		.red {
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   类选择器口诀：
	<div>差异化选择，</div>
	<div class="red">一个或多个。</div>
	<div>上面点定义，</div>
	<div>类名别写错。</div>
	<div>谁用谁调用，</div>
	<div>class来做。</div>
	<div class="red">嘿嘿，工作类最多。</div>
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